Consumers use paper wiping products, such as tissues, for a wide variety of applications. For example, various types of tissues can be used, such as facial tissues, bath tissues, paper towels, napkins, etc. In many instances, various types of compositions, such as softening compositions, lotions, friction reducing agents, adhesives, etc., are also applied to the tissue. For example, a tissue can be softened through the application of a chemical additive (i.e., softener). However, one problem associated with some conventional softeners is the relative difficulty in applying the softeners to a tissue.
For instance, many softeners are made as an emulsion containing a particular solids content in solution. However, such solutions are often difficult to adequately apply to a tissue. In particular, when applying such a solution, the tissue can become undesirably saturated, thereby requiring the tissue to be dried. Moreover, it is also difficult to uniformly spread the solution on a tissue in such a manner to provide adequate surface area coverage. In addition, some softeners contain components that cause the composition to be formed as a solid or semi-solid. To facilitate application of these compositions onto a tissue, extensive heating may be required. Moreover, even after extensive heating, it may nevertheless be difficult to uniformly apply the composition to the tissue surface.
As such, a need currently exists for an improved method of applying a composition, such as a softening composition, to a tissue.
The present invention is generally directed to a method of foaming a liquid-based composition onto a tissue. For example, in one embodiment, a liquid-based composition containing a hydrophilic softening composition can be foamed onto a tissue in accordance with the present invention.
A foam composition of the present invention can generally be formulated in a variety of ways. For instance, in one embodiment, the foam composition is formed from a combination of a liquid-based composition and a gas, such as air. Additional components, such as foaming aids, water, odor control agents, etc., can also be incorporated into the liquid-based composition so long as such components do not adversely affect the ability of the liquid-based composition to form into a foam composition.
To form a foam composition from the above-mentioned components, any of a variety of foam generating devices can be utilized. In one embodiment, for example, a foam generator can be utilized that rotates at a certain speed so as to cause the liquid to pass through a series of edges, allowing the trailing eddy currents of air to entrain into the liquid. In particular, one suitable foam generator that can be utilized in the present invention can be obtained from Gaston Systems, located in Stanley, N.C.
When forming the foam composition, it is typically desired that the flow rates of the liquid-based composition stream and the air stream entering the foam generator be controlled. By controlling the flow rates of the foam components, the characteristics of the resulting foam composition may also be controlled. For example, the xe2x80x9cblow ratioxe2x80x9d, i.e., the ratio of air volume to liquid volume, can be maintained at a certain value by controlling the flow rates of the liquid and air streams. Specifically, in most embodiments, the foam composition of the present invention has a blow ratio greater than about 3:1, and particularly between about 5:1 to about 180:1. For example, in one embodiment, the blow ratio can be between about 150:1 to about 180:1, while in another embodiment, the blow ratio can be between about 15:1 to about 25:1.
In addition to the blow ratio, control over the component flow rates can also allow the foam to be generally stable before being applied to the tissue. In particular, the foam composition of the present invention can have a half-life greater than about 3 minutes, particularly between about 3 minutes to about 30 minutes, and more particularly between about 15 minutes to about 25 minutes.
Once the foam composition is formed, it can then generally be extruded onto a moving fibrous web utilizing any of a variety of foam applicators. For example, in one embodiment, a foam applicator having a distribution chamber and an extrusion head can be utilized. In general, the distribution chamber can have any shape or size. In one embodiment, for example, the distribution chamber has a parabolic shape. Moreover, the extrusion head can also generally have any shape or size. For example, in one embodiment, the extrusion head has a straight-slot shape.
By foaming a composition onto a fibrous web in accordance with the present invention, tissue products having a variety of characteristics can be formed. For example, in one embodiment, a tissue having elevated regions and non-elevated regions can be applied with a foam composition of the present invention. In particular, by controlling various characteristics of the foam composition as described herein, the foam can be applied such that the liquid-based composition is uniformly deposited on the elevated regions of the surface of a tissue. Specifically, the liquid composition can be deposited such that a greater amount of the composition resides on the elevated regions of the tissue to impart certain characteristics thereto. In one embodiment, for instance, a hydrophilic, softening composition can be foamed onto the elevated regions of a tissue to provide an improved soft feel to the tissue surface. In some embodiments, the application of the hydrophilic composition to only the elevated regions can allow the tissue to possess discrete hydrophilic portions.
Other features and aspects of the present invention are discussed in greater detail below.